The present invention relates to fluid transport equipment, such as a marine loading arm, and, more particularly, to mechanism to maintain the attitude of a portion of the arm.
Marine loading arms usually comprise rigid fluid conducting conduits pivotally connected in end to end relation to form an articulated member for conveying oil or other fluid to or from a vessel. Frequently, one or more sections of the arm is driven by a motor to position the arm in a desired position for loading or unloading a ship.
It is sometims desirable, during loading or unloading, to maintain an outer arm section in a fixed attitude regardless of the position of the inner section of the loading arm.
The attitude maintenance mechanism usually employed in the prior art consists of a cable and sheave construction as shown, for examle, in the U.S. Pat. No. 3,889,728. In this type of construction the sheaves are mounted, respectively, at the inner and outer ends of the inner arm, and the outer sheave is generally connected to the member which is to be maintained in a particular attitude. The inner sheave is generally fixed so that when the inner arm is raised or lowered, the outer sheave is rotated by the endless cable and rod assembly connecting the sheaves to maintain the member connected thereto in the desired attitude. Although parallel rods are used in U.S. Pat. No. 3,889,728, they are used only to interconnect sections of the cable. In this type of construction, the outer arm section will remain in the desired attitude so long as the outer sheave does not slip with respect to the cable.